1. Field of the Invention
The invention relates to an individual source identification of several signal providers or pick-ups with closable contacts disposed in a twin-wire signal line, in particular for fire detectors in fire alarm systems.
2. Brief Description of the Background of the Invention Including Prior Art
Signal contacts are employed in many application areas in case of process controls, of measurement and control systems, as well as in case of automatic fire-extinguishing systems, which signal contacts signal the proper function or the position of the final function control members.
If several of such signal contacts are employed in a system, then it is required, in case of a signal deviating from the standard situation, that the place of interference be recognized as soon as possible. This can be performed with an optical display placed at each contact or by a remote transmission of the detector identification.
Optical displays disposed at detectors can be realized in a relatively economic way. However, in large systems where, for example, 100 and more signals are employed, the searching for an optical display of an actuated or responding signal detector is fairly timeconsuming. Other systems lead a line from each signal contact to a central location. A quick identification is thereby possible. However, the expenditure of installing such a system is substantial.
As a consequence of this measure, each detector comprises only one contact and two inexpensive passive device elements. Several such detectors can be disposed in an unprotected twin-wire signal line. In this case, each released detector has the value "1", where this value is increased depending on the sequence of the detectors disposed in the signal line, respectively, by the number of the detectors disposed in the course of the signal line ahead of the actuated or responding detector. This means that in each signal line with, for example, ten detectors, in case of an actuation the detector disposed at the sixth position sends a message with the value six to the central station. The same situation occurs with the remaining detectors. The evaluation circuit can display the value digitally or analog or can, with a corresponding program, be furnished as an alphanumeric output.
A later increase or decrease of the number of detectors is possible without interfering in the detectors or in the evaluation device.